<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    body{
      margin: 0;
      padding: 0;
      background-image: url(../images/grid.png);
    }
    .box{
      position: relative;
      width: 200px;
      height: 100px;
      background-color: skyblue;
      
      /* 在父元素添加透视效果 */
      perspective: 800px;
    }

    .item{
      position: absolute;
      top: 0;
      left: 0;
      width: 100%;
      height: 100%;
      background-color: pink;
      /* 形变 */
      /* transform: rotateY(180deg); */

      /* 元素背向是否可见 */
      backface-visibility: hidden;

      /* 帧动画 */
      animation: loop 6s linear infinite;
    }

    @keyframes loop{
      0%{
        transform: rotateY(0deg);
      }

      100%{
        transform: rotateY(-360deg);
      }
    }
  </style>
</head>
<body>
  
  <div class="box">div
    <div class="item">10</div>
  </div>
</body>
</html>